Combined rolling and extruding method and the device for performing the same

Abstract

A method for combined rolling and extruding of cast billet is proposed. When implementing the method for combined rolling and extruding of metals or alloys, a cast billet with a predetermined temperature is fed to the working gauge, in which it is rolled and then to the die, through which the cast billet is extruded. When the cast billet is fed into the working gauge, a cladding layer of metal or alloy is created on the surfaces of the rolls by extruding the cast billet through the gaps formed between the surfaces of the rolls and the die. This invention makes it possible to improve the quality of the resulting products, as well as to increase the efficiency of the process as a whole.

Claims

1. A method for combined continuous casting, rolling, and extrusion of a metal billet, including the following steps: forming and crystallizing a continuous cast billet in a mold, regulating the temperature of the cast billet, and rolling the cast billet with a preset temperature in a working gauge formed by two rolls and then extruding the cast billet through a die, wherein the continuous cast billet is rolled so that gaps are formed between working surfaces of the rolls and working surfaces of the die, wherein a metal of the cast billet, when the cast billet is fed into the working gauge, is extruded through the gaps to form a cladding layer of metal on surfaces of the rolls.

2. The method described in claim 1, according to which the billet is extruded with an elongation ratio of 5.2 to 16.8.

3. The method described in claim 1, according to which the mold is a rotary mold and metal is fed into the mold horizontally.

4. The method described in claim 1, according to which the temperature of the continuous cast billet, before the cast billet is fed into the working gauge, is 380 to 420° C.

5. The method described in claim 4, according to which the temperature of the continuous cast billet, before the cast billet is fed into the working gauge, is 400 to 420° C.

6. The method described in claim 1, according to which the cast billet is inductively heated when the temperature of the continuous cast billet is lower than a set temperature.

7. The method described in claim 1, according to which the cast billet is cooled when the temperature of the continuous cast billet is higher than a set temperature.

8. The method described in claim 7, according to which the billet is cooled by supplying some coolant on to a surface of the billet.

9. The method described in claim 1, according to which the continuous cast billet is fed into the working gauge, which is formed by two rolls locked by a die with a calibrated opening at an angle to the die axis or parallel to said axis.

10. The method described in claim 9, according to which the continuous cast billet is fed into the working gauge at an angle of 0 to 20 degrees to the die axis.

11. The method described in claim 1, according to which the continuous billet is formed from aluminum or an aluminum alloy.

Description

(1) The invention essence is explained by the drawings.

(2) The schematic view of the device is shown in FIG. 1

(3) The schematic diagram of the groove-fin connection in section of the rolls is shown in FIG. 2.

(4) The schematic diagram of the die-grooved roll section is illustrated in FIG. 3.

(5) The schematic diagram of the die holder-die connection section is shown in FIG. 4.

(6) The fin geometric dimensions ratio is shown in FIG. 5.

(7) The die geometric dimensions ratio is described in FIG. 6.

DETAILED DISCLOSURE OF THE INVENTION

(8) The combined rolling and extruding device (FIG. 1) includes:

(9) a holding furnace 1 with liquid aluminium or aluminium alloy 2, a rotary mould 3 forming a cast billet 4 of an infinite length, a temperature control device 5 for the cast billet, the rollers of a guide element 6, a grooved roll 7 and a finned roll 8 and a die 9 forming a closed working gauge (FIG. 2) for extruding a semi-finished product 10, and a semi-finished product cooling device 11.

(10) The cylindrical surface of the grooved roll 7 is provided with fins 12 coupled with grooves 13, made on the cylindrical surface of the finned roll 8. The said fins and grooves on the surface of the rolls 7 and 8 form a labyrinth coupling of the said rolls with each other. During the operation of the unit, a deformation zone is created inside the working gauge due to the active friction forces. A fin 14 of the roll 8 has a T-shaped working surface at the site of mating with the deformation zone (shaded area in FIG. 2). The T-shaped fin of the roll 8 is positioned with respect to the groove of the roll 7 with the possibility of forming a gap K between the side surfaces of the groove of the roll 7 and the contact surfaces of the fin of the roll 8 (FIG. 2). The width of the gap K is of 0.2 to 0.5 mm. Between the contact surfaces of the groove of the roll 7 and the non-contact surfaces of the fin of the roll 8, a gap L equal to 2.0-3.0 mm is provided. The T-shaped fin of the roll 8 (FIG. 5) has a ratio of the height of the belt c to the width of the fin b equal to 0.07-0.08.

(11) The die 9 (FIG. 3) has a T-shaped working surface 14 coupled with the deformation zone and the side surfaces of the roll 7. At the same time, between the side surfaces of the roll 7 and the contact surfaces of the die 9, a gap M with a width of 0.2-0.5 mm is provided. Between the contact surfaces of the groove of the roll 7 and the non-contact surfaces of the die 9, a gap N equal to 2.0-3.0 mm is provided.

(12) The working part of the die (FIG. 6) has a ratio of the height of the belt d to the width of the die e equal to 0.08-0.09.

(13) The die 9 (FIG. 4) and the die holder 15 have the mating rectangular fins and grooves designed to prevent rotation of the cylindrical part of the die 9 relative to the die holder 15.

(14) The die holder provides installation of the die in the working gauge with a gap G between the following surfaces: the top of the fin of the roll—the die and the bottom of the groove of the roll—the die equal to 1 to 2 mm.

(15) Due to the presence of the gaps between the working surfaces of the rolls and the working surfaces of the rolls and the matrix, the contact between the steel surfaces is excluded, which increases their service life. In the process of extrusion, a cladding layer of metal or alloy, for example, aluminium or its alloy, is formed on the contact surfaces of the rolls thereby increasing the power of the active friction forces due to the metal-metal friction coefficient, in a particular case, this can be a cladding layer of aluminum-aluminum. At the same time, the die forms a cladding layer of metal on the rolls by the faces of its working surfaces.

(16) The thickness of the metal or alloy cladding layer on the working surfaces of the groove and the fin of the rolls 7 and 8 is equal to 0.2 to 2.0 mm.

(17) As was already mentioned, the T-shape of the working part 14 of the die 9 allows creating a gap G between the side surfaces of the groove and the contact surfaces of the die. Due to the presence of a gap M between the side surfaces of the groove and the contact surfaces of the die and the die holder, and the rigid positioning of the die 9 relative to the die holder 15 and the rolls 7 and 8, the steel-to-steel contact is excluded and the wear of the die is reduced.

(18) As was already mentioned, the T-shape of the die also ensures the presence of gaps N between the side surfaces of the groove and the non-contact surfaces of the die and the die holder. The presence of the gaps M and N eliminates formation of the ridge and loss of metal from the working gauge in the die-groove mating during extrusion.

(19) Internal cooled channels are made around the entire circumference of the rolls 7 and 8.

(20) The coolant supply and removal channels are installed at the outlet of the die 9.

(21) The device 5 of temperature control of the cast billet provides the billet optimum temperature of 380-420° C. to ensure the stable extruding process and stable properties of the extruded long semi-finished products regardless of the casting conditions and the cast billet temperature at the outlet of the mould. The temperature stabilisation device is a combined assembly consisting of an inductor (for heating the cast billet at a temperature below the nominal) and a cooler (for cooling the cast billet at a temperature above the nominal). Heating of the cast billet is carried out by induction heating; cooling of the cast billet is carried out by irrigation. Control of the set temperature of the cast billet is carried out in a contactless way, for example, using a pyrometer. The set temperature of 380-420° C. provides sufficient strength of the cast billet in the hot state for its accurate positioning in the working gauge of the rolls 7 and 8 by the guide device 6.

(22) From the holding furnace 1 metal or metal alloy (for example, aluminium or aluminium alloy) 2 is horizontally fed to the rotary mould 3, in which a continuous cast billet 4 is formed. The cast billet 4, after passing through the temperature stabilisation device 5 and the rollers of the guide element 6, enters the working gauge formed by the rolls 7, 8. The guide element 6 provides the cast billet feeding into the rolls at an angle α to the extrusion axis ranging from 0 to 20°. At the same time, by maintaining the optimum temperature of the cast billet 4 and selecting the optimal angle α of the cast billet to the extrusion axis, the stability of the process of feeding the cast billet into the roll gauge is ensured. The cast billet 4 is captured by the rolls 7 and 8, due to the active friction forces in the working gauge, extruded through the calibrated opening of the die 9; the resulting extruded semi-finished product 10 is cooled in the cooling device 11. The T-shape of the fin 14 of the roll 8 provides a gap K between the side surfaces of the roll 7 and the contact surfaces of the fin of the roll 8, a gap L between the side surfaces of the grooves of the roll 7 and the non-contact surfaces of the fin of the roll 8. Thanks to this, the steel-to-steel contact in the groove-to-fin mating is eliminated and the rolls wear is reduced. In the process of extrusion, the metal or alloy, coming out of the gauge formed by the rolls 7 and 8 locked by the die 9, fills the gap L, at the same time due to the presence on the cylindrical surfaces of the labyrinth formed by the fins 12 of the roll 7 and the grooves 13 of the roll 8; further metal exit from the gauge is excluded. Thus, the formation of the ridge and loss of metal from the working gauge is excluded thanks to the self-sealing of the groove-to-fin mating by the layer of aluminium or alloy formed in the gap L.

(23) Thanks to this invention, when implementing the combined rolling and extruding process, the return loss of metal is reduced, the energy consumption of the process is reduced, the quality and homogeneity of the extruded semi-finished products is increased, and the performance is increased.

(24) An Example of a Specific Implementation of the Method and Device.

(25) As an example of practical use of the device, an example of deformation of a continuous cast billet on the experimental industrial line LPA 6 is given. Casting with obtainment of a continuous cast billet of 40λ37 mm in section was carried out in a rotary mould with a diameter of 1,510 mm. Continuous combined rolling and extruding was carried out on a CREP unit with the diameter of the cooled rolls of 428 mm with the rotation speed of the rolls of 3 to 12 rpm. The melt temperature was 750° C.; the temperature of the cast billet at the outlet of the rotary mould was 520° C.; the temperature of the cast billet after the temperature stabilisation device at the inlet to the gauge was maintained in a range of 380-420° C. A heat-resistant Al—Zr alloy was used containing the following % wt.: 0.1 of silicon; 0.25 of iron; 0.28 of zirconium; the rest was aluminium. Extrusion was carried out by means of dies with extrusion ratio μ of 5.2 to 16.8 followed by cooling and winding of the extruded bar. A pilot batch of 9.5 mm wire rod of Al—Zr alloy in the volume of 6 t was obtained. Samples for tensile strength and electrical conductivity testing were cut from the extruded bars; their ultimate tensile strength σ, relative elongation δ, and specific electrical conductivity were estimated based on the test results. The obtained coils were subjected to thermal annealing. After thermal annealing, the samples were taken for tensile strength and electrical conductivity testing. The test results of the samples of the extruded bar and the wires are given in table 1.

(26) TABLE-US-00001 TABLE 1 Ultimate tensile Electrical Relative strength resistance, elongation δ, Sample condition (σt), MPa Ohm * mm.sup.2/m % Bar of 9.5 mm in 147.5 0.03357 6 diameter after extrusion Bar of 9.5 mm in 127.9 0.02799 19.5 diameter after extrusion and thermal annealing

(27) Thermal treated coils of the extruded bar were further drawn into a wire down to 3.50 mm in diameter. Wire drawing was performed on a wire-drawing machine without slippage. The drawing speed on the diameter of 3.50 mm was of 7.21 m/sec. Lubricating and cooling fluid was used to lubricate the drawing dies. The drawing sequence was as follows: 9.5-8.0-6.92-5.93-5.04-4.32-3.71-3.50.

(28) The test results of wires of 3.50 mm in diameter are given in table 2

(29) TABLE-US-00002 TABLE 2 Ultimate Electrical tensile strength resistance, Relative Sample condition (σt), MPa Ohm * mm.sup.2/m elongation Δ, % Wire of 3.50 mm 184 0.027615 2.5 in diameter after drawing

(30) After drawing, 15 samples of wires with a diameter of 3.50 mm were selected for thermal stability tests. Heat treatment of the wire samples was carried out in a laboratory furnace at temperatures of 230, 280, and 400 during 1 hour. After heat treatment, the samples were air cooled.

(31) The results of the tests of the mechanical properties and electrical conductivity of the heat treated wires are given in table 3.

(32) TABLE-US-00003 TABLE 3 230° C. 280° C. 400° C. Wire size Ultimate tensile Ultimate tensile Ultimate tensile (mm) strength (σt), MPa Softening, % strength (σt), MPa Softening, % strength (σt), MPa Softening, % 3.50 180 97.8 179 97.3 161 90.0

(33) Thus, the test results showed that the wire made of Al—Zr alloy wire rod obtained by the proposed method for combined rolling and extruding meets the requirements of AT1, AT3, and AT 4 types of the international standard IEC 62004.